Comments

From: Kevin Wolf <kwolf@redhat.com>
Now that we do not have to flush the backing device anymore implementing
the bdrv_aio_flush method for image formats is trivial.
[hch: forward ported to qemu mainline from a product tree]
Signed-off-by: Kevin Wolf <kwolf@redhat.com>Signed-off-by: Christoph Hellwig <hch@lst.de>